1. Statement of the Technical Field
The inventive arrangements relate generally to the field of satellite systems, and more particularly to systems for mitigating the limitations of onboard satellite data recorders.
2. Description of the Related Art
Earth satellites are used for a wide variety of civilian and military purposes. In the civilian realm, these purposes can include weather, communications, mapping, and resource exploration. Satellite operators often assign certain predefined tasks to an orbiting satellite. These tasks can include memory intensive applications including the collection of data such as imagery, signal handling, and so on. A list of targets for data collection often must be predefined by the operator as the satellite may not always be in range of a ground control station. The data is generally recorded to a computer memory device and then relayed to a ground station at a convenient time.
In recent years, state-of-the-art electronics provide satellites with greater memory capacity and flexibility through the use of solid state recorders (SSRs). These SSRs can have a greater capacity as compared to older electro-mechanical systems such as tape drives. They also offer greater flexibility as compared to less advanced systems by permitting record and play back of data simultaneously. Another advantage of the SSR is the ability to record multiple data streams at the same time. Further, data recorded to an SSR can be instantly accessed.
One problem encountered by satellite operators relates to the selection of targets and the limited available data memory/storage on-board the spacecraft. In particular, satellite operators often desire to increase the list of potential targets without exceeding the limited data storage capacity available on-board the spacecraft. Despite the many advantages of the SSR, the total volume of data that can be stored often remains a limiting factor.
In conventional satellite systems, a list of selected targets is uploaded to the satellite. The satellite then acquires the data in a serial fashion. As noted above, the operator who compiles the list is limited by the satellite data storage capacity. In an effort to address these considerations, current state-of-the-art satellite targeting systems conventionally make use of a decision tree of targets to acquire based on several factors. These factors can include 1) mission priority, 2) spacecraft momentum considerations, 3) weather, and other factors. Consequently, high priority targets can in some instances be eliminated from the target list if the probability of successful acquisition is deemed to be low. Further, some data that is acquired may later be deemed to be of little or no value if, when the satellite arrives at the target, it is discovered that the target is absent from its anticipated location, obscured, and so on. Despite the absence of useful information, data is acquired at the target location and stored in the satellite's storage, thereby wasting valuable memory resources.
In the past, satellite resources have been considered so valuable that even completely useless data has been saved for future, unknown uses. The paradigm has been that nothing should be discarded. Further, data processing onboard satellites has been relatively minimal in the past. Consequently, the ability to diagnose the usefulness of the acquired data was essentially non-existent. Further, many prior art data recorder systems used on board satellites have not had the ability to rewind and overwrite data without interrupting satellite operations. Accordingly, there was no practical ability to review and discard data in real time.